Towards a deeper understanding of catalytic activity in supported precious metal catalysts

负载型多相催化剂由分散在氧化物载体(即SiO_2/Al_2O_3)上的纳米金属/金属氧化物(如铬、镍、钴、金、钯、铂和银)组成，在估计价值约1,500亿美元/年的行业中发挥着核心作用。它们是通过核心催化过程(即聚合、异构化、还原和氧化)将天然气和天然气的馏分转化为各种日常使用化学品的主要参与者。供应的减少和对这些原料需求的增加意味着催化剂和催化过程尽可能高效地运行是至关重要的。最佳效率通常是通过将结构和功能合理化来实现的，并形成了许多催化研究的基础。然而，进行的表征通常是不完整的，很少在反应条件下进行，这导致了关于是什么使催化剂具有活性的相反的结论。该项目将通过关联影响催化剂性能的参数，如纳米颗粒尺寸、形状、氧化还原功能和金属-载体相互作用，在加氢和氧化的核心催化过程中影响和演变，建立更强大的结构-活性关系。该项目采用了一种新的方法，利用催化剂制备和原位催化剂表征的技术，制备了沉积在平板氧化物载体上的尺寸可控的单金属纳米颗粒，并使用同步时间分辨掠入射X射线散射(GIXRS)技术对它们进行了表征。特别是，将使用小角/广角掠入射散射法(GISAXS/GIWAXS)，但也将尝试从数据中提取对分布函数((GI)PDF)，以便能够更完整地表征催化剂。这种彻底的表征以前从未被采用过，将被用来确定两相(氢化)和三相(氧化)催化体系中催化纳米颗粒的显著特征。预计这些测量将被证明是非常有价值的，以了解什么是支撑的纳米颗粒滴答，并为未来的催化剂优化和设计的重要基础。

Supported heterogeneous catalysts comprising nano-sized metals/metal oxides such as Cr, Ni, Co, Au, Pd, Pt and Ag dispersed on an oxide support (i.e. SiO2/Al2O3), play a central role in an industry estimated to be worth ca. 1500 billion $US/annum. They are the principle protagonists in the conversion of fractions from natural oil and gas to produce, via core catalytic processes (i.e. polymerisation, isomerisation, reduction and oxidation), a wide variety of chemicals for everyday use. A combination of dwindling supply and increasing demand on these feedstocks means it is vital that catalysts and catalytic processes operate as efficiently as possible. Optimal efficiency is normally achieved by rationalisation of structure with function and forms the basis for much catalysis research. However the characterisation performed is often incomplete and rarely performed under reaction conditions leading to contrasting conclusions as to what makes a catalyst active. This project will develop more robust structure-activity relationships by correlating how parameters that influence catalyst performance i.e. nanoparticle size, shape, redox functionality and metal-support interactions, affect and evolve in core catalytic processes of hydrogenation and oxidation. The project adopts a novel approach drawing on skills in catalyst preparation and in situ catalyst characterisation to prepare size-controlled monometallic nanoparticles, deposited on a flat oxide supports and to characterise them in operando using simultaneous time-resolved grazing incidence X-ray scattering (GIXRS) techniques. In particular small angle/wide angle grazing incidence scattering methods (GISAXS/GIWAXS) will be used although attempts will also be made to extract pair distribution function ((GI)PDF) from the data to enable a more complete characterisation of the catalyst. Such a thorough characterisation has never been previously employed and will be used to determine the salient characteristics of catalytic nanoparticles in both two-phase (hydrogenation) and three-phase (oxidation) catalytic systems. It is expected that these measurements will prove invaluable for understanding what makes a supported nanoparticle tick and an important basis for future catalyst optimisation and design.